Two types of highly repeated DNA segments in the genome of the African green monkey (Cercopithecus aethiops) are being studied: (1) Satellite DNAs are characterized by long tandem repetitions and centromeric location. Earlier work indicated that the organization of one monkey satellite, deca-satellite, is highly polymorphic in individual members of the species and undergoes frequent rearrangement in cell culture. Recent data show in addition that the amounts of deca-satellite and alpha-satellite, the major monkey satellite, vary (independently) in individual genomes. In an effort to understand the maintenance of such extensive but variable DNA sequences, analysis of junctions between satellite and unique genomic sequence has been initiated; several such DNA segments have been cloned and partially characterized. (2) Previous experiments showed that the KpnI family of long interspersed repeats has members ranging from a few hundred to 6 kbp in length. Cloning and analysis of several new full-length members with surrounding sequences established the sequence at the 2 ends of the element. No terminal repeats occur and while some family members are flanked by target site duplications, others are not. The designated 3'-end varies some but generally includes a polyadenylation site. Assembling data from this and other labs, a sequence for the full 6 kbp was compiled. The sequence contains at least 3.5 kbp of open reading frame, ending 200 bp upstream from the polyadenylation site, at the same position where the previously described homology between the KpnI family and its rodent homologue stops. We conclude that the KpnI family is likely to consist of one or more functional genes as well as pseudogenes. Although transcripts of KpnI family sequences are abundant in the nucleus (and heterogeneous in size), many monkey and human cell lines fail to show significant amounts of homologous polyadenylated cytoplasmic RNA. One cell line revealed such an RNA band about 6 kb long.